如何使用post請求下載檔案

使用get請求下載檔案非常簡便，但是get請求的url有長度和大小的限制，所以當請求引數非常多時無法滿足需求，所以改成post請求
const res = await fetch(`xxxxxxxxx`, {
  method: `post`,
  body: JSON.stringify(params),
  credentials: `include`,
  headers: {
    `Cache-Control`: `max-age=0`,
    `Pragma`: `no-cache`,
    `Content-Type`: `application/json;charset=UTF-8`,
    `x-requested-with`: `fetch`
  }
  });
  const blob = await res.blob();
  if (`download` in document.createElement(`a`)) {
  var a = document.createElement(`a`);
  a.style.display = `none`;
  var url = window.URL.createObjectURL(blob);
  var filename = decodeURIComponent(res.headers.get(`Content-Disposition`));
  a.href = url;
  a.download = filename;
  document.body.appendChild(a);
  a.click();
  window.URL.revokeObjectURL(url);
  document.body.removeChild(a);
  } else {
  navigator.msSaveBlob(blob);
}